arm: koelsch: Disable TMU0 before OS boot

On U-boot uses TMU0 as timer, but TMU0 does not use on linux kernel
and other.
This disables TMU0 at the request of from kernel user.

Signed-off-by: Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@renesas.com>
Signed-off-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>